As a member used under a plasma irradiation environment such as a semiconductor manufacturing apparatus, a member having a highly plasma resistant coat formed on the surface of the member is used. The coat is based on, for example, an oxide such as alumina (Al2O3), yttria (Y2O3) or the like, or a nitride such as aluminum nitride (AlN) or the like.
On the other hand, in an oxide-based ceramics, a volume of a film expands and a crack or the like occurs with fluoridation due to a reaction with a CF-based gas, and as a result, particles are generated, therefore use of fluoride-based ceramics such as originally fluoridated yttrium fluoride (YF3) or the like is proposed (JP 2013-140950 A (Kokai)).
On the reason that although YF3 is highly resistant to an F-based plasma, YF3 is insufficiently resistant to a Cl-based plasma, or chemical stability of fluoride is doubtful, use of a thermal spray film or a sintered body of yttrium oxyfluoride (YOF) is proposed (JP 2014-009361 (Kokai), JP 2016-098143 A (Kokai)).
For example, it is also considered that a thermal spray film is formed by using oxyfluoride of a rare-earth element as a source material (Japanese Patent No. 5927656). However, in the thermal spray, the film is oxidized by oxygen in the atmosphere upon heating. Therefore, Y2O3 may be mixed in the obtained thermal spray film and control of compositions may be difficult. The thermal spray film has yet a problem in denseness. There is a problem that if a chamber with YF3 coated by a thermal spray or the like is used in plasma etching, an etching rate drifts and is unstable (United States Patent Application Publication No. 2015/0126036). It is also discussed that after forming a film including Y2O3, the film is fluoridated by annealing such as plasma treatment or the like (United States Patent Application Publication No. 2016/273095). However, since fluoridation treatment is performed to film including Y2O3 in this method, there is a fear that a trouble occurs, namely, a volume of the film may change by fluoridation and may be peeled off from a base, or a crack occurs in the film. It is also difficult to control a composition of the whole film. In the thermal spray film and the sintered body, F2 gas is released by thermal decomposition of fluoride source material fine particles during heating, and there is a problem in safety.
On the other hand, JP 2005-217351 A (Kokai) discloses that it is possible to form the highly plasma resistant structure of Y2O3 at a normal temperature by an aerosol deposition method. However, the aerosol deposition method using yttrium oxyfluoride has not been discussed sufficiently.